In semiconductor devices in which an aluminum electrode is provided in contact with a semiconductor substrate, heat treatments such as reflow soldering and sintering treatments performed after the formation of the aluminum electrode can sometimes cause mutual diffusion between the silicon (Si) of the semiconductor substrate and the aluminum (Al) of the electrode, resulting in Al spiking. One known technique for suppressing this Al spiking involves using an Al—Si electrode in which the layer of the electrode that contacts the semiconductor substrate is formed from a film of an aluminum-silicon (Al—Si) alloy. By using such an Al—Si electrode, the occurrence of Al spiking in electrodes provided in contact with the semiconductor substrate is suppressed.
On the other hand, when an Al—Si electrode is used, another problem arises in that following the types of heat treatments described above, the Si that does not undergo solid dissolution in Al may precipitate, forming Si nodules. These Si nodules formed at the interface between the electrode and the semiconductor substrate reduce the effective surface area of the electrode, and may also be retained following etching of the Al.
In JP S64-71176 A, in order to suppress the formation of Si nodules, a wiring electrode formed from a film of an aluminum-silicon-titanium (Al—Si—Ti) alloy is connected to a semiconductor substrate with a metal silicide film disposed therebetween. In the semiconductor device of JP S64-71176 A, the precipitated Si is reacted with the Ti and consumed as titanium silicide (TiSix), thereby suppressing Si deposition.